Description of Related Art
In the manufacture of cellulose pulp sheet material, and more particularly in the drying thereof, a moist pulp sheet in continuous form is progressed in serpentine manner about a plurality of rollers provided within a closed dryer, the sheet being of sufficient inherent rigidity to maintain its integrity, although a degree of support may be provided by pulsed air within the dryer. Conveniently the sheet is advanced by applying a drive motion to one or more of the rollers existing within the dryer although other drive rollers may be provided if preferred.
At the start up of production, or in the event of sheet breakage, the pulp sheet width is temporarily reduced to provide a tail which is fed through the dryer section. Gradually, as the tail proceeds along the circuit the sheet width is increased until a full-width state is reached. The guiding mechanism for the pulp sheet tail is the woven fabric, the subject of the present invention, the fabric being in folded V-form and engaging the edge of the pulp sheet and pulling such sheet along the circuitous dryer path. The guide fabric is in the form of a closed loop, and tension and guiding mechanisms therefor are provided in that run thereof which exists externally of the dryer.
When the pulp sheet has been widened to full width and this part is starting to leave the dryer, the guide fabric is normally pulled away from the sheet and is then "parked" in a stationary position until it is re-utilized on a later occasion. In an alternative arrangement, the pulp sheet is cut at a position just along the outside edge of the guide fabric, so that, in effect, the sheet is shifted across the machine width by the width of the guide fabric. The drying of the pulp sheet is effected by circulation of hot dry air within the dryer.
The nature of the pulp sheet and the high moisture content thereof necessitates a dryer run of significant proportions and fabrics of the kind to which the invention relates are typically 1 kilometer in length.
Dimensional stability of the fabric in the lengthwise direction thereof is particularly important and, in view of the significant length of the fabric involved, difficulty is experienced in producing a fabric capable of maintaining its length within acceptable limits.
It is known that, contrary to previous indications, paralinked aramid yarns are of application in the field of papermachine and like clothing notwithstanding their susceptibility to physical damage and the adverse effect thereon of extended exposure to heat and moisture. It has, however, hitherto been thought necessary to provide some form of insulation of the paralinked aramid yarns against the adverse effect of extended exposure to heat and moisture by locating such yarns within the body of the fabric, and more particularly by providing the paralinked aramid yarns within a core of yarns, ad prior proposals have been directed accordingly.